Have you ever seen how mad people get at each other on the road? Yeah, people suck when they don't have a face in front of them to remind them its a person on the other side. It's disingenuous to pretend that side of people doesn't exist though.
Maybe, but that itself (just like downvote brigading) is a technique used to suppress discussion. Become so "outraged" when others simply state their opinion to make normal discussion impossible.
That is an area in which I don't think HN moderation does a good job. They blame people who merely state a controversial opinion for "initiating a flamewar" instead of standing firm against the angry mob and putting emphasis on the importance of keeping a high standard for discussion. Simply being outraged is quite diagonal to curiosity, the core value of HN.